The present invention relates to irrigation control as well as water and energy savings, and more particularly to methods and apparatus for use with existing controllers that are capable of implementing time of use (TOU) governmental landscape watering restrictions that override the operational schedule of such controllers.
1. Field of the Invention
In order to conserve water, the irrigation industry, state government water related agencies, and local water districts have encouraged for several years the use of smart irrigation controllers to save water. Smart controllers are referred to as controllers that can adjust their irrigation schedule depending upon local environmental conditions such as temperature, relative humidity, solar radiation, and wind. These irrigation related measures have been taken because western states frequently experience drought conditions, making water supplies critical. Residential landscape irrigation accounts for 50% to 70% of all residential water use in California, Nevada, and Arizona. Current attempts to generate public education and interest for water conservation using “smart” irrigation controllers and modules that adjust themselves to accommodate for varying environmental conditions throughout the year have not proven effective. While theoretically irrigation efficient, they have not solved the problem of conserving water due to their extremely low voluntary user and installer participation.
For example, the Los Angeles Metropolitan Water District (MWD) and its associated water districts provide water to 3.5 million residential and commercial customers in Southern California. To promote water conservation, the MWD has been promoting the use of “smart” irrigation controllers that adjust themselves to changing daily weather conditions, since customers generally fail or forget to adjust their non-smart irrigation controllers on their own. MWD's associated water districts have either provided a variety of smart controllers from well-known manufacturers either free of charge, or rebated up to 100%. The MWD reports that after 3 years of their smart controller rebate programs, less than 10,000 customers of the 3.5 million have tried to use these smart controllers. Of these, it is estimated that no more than 50% are properly used in their smart mode. This translates to far less than 1% effective usage, which would produce minimal water conservation. Another large water district, the Southern Nevada Water Authority (SNWA—which, includes Las Vegas, Nev.), reports that in over two years, fewer than 100 controllers have been rebated in an area encompassing about 500,000 addresses. Other water districts report similarly poor response to smart controller programs. Some reasons for these mediocre results are set forth below:                1. Programming ET-based (ET=evapotranspiration) smart controllers can be complex. In addition to conventional programming that requires entry of watering days, start times and watering durations, ET-based controllers require entries of precipitation rates, crop coefficient factors, soil type, slope, percentage of shade, and/or other information which is not readily available to homeowners.        2. ET-based systems, which account for many smart controllers, require either an adjacent weather station, or the transmission of weather data from which ET is calculated or ET itself. The cost of a weather station is typically several times that of the controller. The ET data transmitted to smart controllers (if weather stations are not used) requires monthly service fees that can easily exceed the cost of the water saved.        3. Landscape maintenance contractors are reluctant to install such systems due to the numerous call backs to reprogram or re-explain smart controller programming to their customers.        4. Landscape contractors and landscape maintenance firms hesitate to train their personnel to learn to program as many as 20 different controllers in order for them to explain it to their residential and commercial customers. The high turnover rate of personnel makes it non-cost effective to train their installers.        5. The reluctance for a homeowner to trust tens of thousands of dollars of their landscaping to a controller they do not understand or cannot program.        6. Many ET-based controllers are not compatible with local watering schedules. ET-based controllers accumulate the daily ET value until some threshold is reached and then permit irrigation. The irrigation day determined by the ET-based controller may not be an allowed watering day.        7. Homeowners are used to seeing their controllers start cycles at certain times of the day on certain days of the week. Not observing irrigation causes them to wonder if their system is working.        8. California bill 1881 has postponed the enforcement of its mandatory smart controller requirements to January 2012, removing the urgency to convert to smart controllers.        9. Low cost of water in many areas due to government subsidies.        10. Lax or inadequate enforcement of water rules.        
In recent years, “smart” controllers (that adjust themselves to changing daily weather conditions) have been promoted for landscape water conservation. Different approaches to “smart” irrigation control are disclosed in this inventor's patents and publications (U.S. Pat. Nos. 7,058,478 and 7,266,428 and 2007/0293990); and a wide variety of ET-based patents such as Hopkins U.S. Pat. No. 5,097,861; Marian U.S. Pat. No. 5,208,855; Oliver U.S. Pat. No. 5,870,302; Sieminski U.S. Pat. No. 6,823,239; Addink U.S. Pat. No. 6,892,114; Addink U.S. Pat. No. 6,895,987, and Mecham U.S. Pat. No. 6,314,340, among others. The latter group of smart controllers utilize ET methods which calculate the theoretical amount of water required to properly irrigate various types of landscapes with varying sprinkler precipitation rates and soil conditions. ET has been studied for 50 years and as many as twenty equations have been developed to calculate ET, which is then converted to minutes of watering duration.
Smart water theory as represented by the numerous ET equations is not necessarily accurate. It is therefore possible that more water can be wasted using ET-based controllers because they are more difficult to understand and program than conventional (non-smart) controllers, particularly if the wrong ET equation is used. Highlighting this possibility, Catteano and Upham conducted a study (“Methods to Calculate Evapotranspiration: Differences and Choices”) that showed that four of these recognized ET equations varied as much as 70% from each other at certain times of the year. Thus, not only is ET theory difficult to understand and not practical to use, as noted above, the various ET equations do not agree with each other.
In addition to the shortcomings of ET-based smart controllers, and the general non-agreement between ET equations, the hydraulic parameters upon which ET controllers depend to convert the inches of ET to station run times are not exact either. Entry of the precipitation rate required to calculate the watering duration from an ET value assumes a first time observation and measurement of that precipitation rate, or use of the manufacturers estimated data. The precipitation rate for a specific sprinkler is based upon the system operating pressure, proper operation of the sprinkler, and the operating efficiency of the valve. Every one of these parameters may vary daily. Furthermore, additional construction of homes in developing areas will cause changes in operating water pressure, water supply, pumping capability, and delivery. The efficiency of pumping systems also varies because of the age and maintenance of the pumps. For all of the above reasons, smart ET-based technology is not an exact science, and no amount of theoretical calculations of ET will save real water unless the system is installed, programmed, and operating properly, including the effectiveness of the infrastructure. Fifty years of research has not given us an answer as to which ET method is accurate. Even the modified Pennman-Montieth ET equation (see patent U.S. Pat. No. 7,266,428), generally accepted by most agencies, is considered to over water by at least 20%. A high level of usage of ET or smart systems, in theory could help conserve water, but does little to address energy, pumping and delivery issues.
Separate from the need for water conservation, to address infrastructure shortcomings such as pumping, water delivery, and operating water pressure, some communities have limited the hours and days of allowable irrigation by specifying, for example, even or odd street address watering schedules, watering groups, times during the day when watering is prohibited, limiting watering to even or odd calendar days, or certain interval(s) of days, etc. In most instances, after an initial education period, these methods have proven to be easier to adhere to and more effective in water conservation than smart controllers. The problem with this voluntary approach is that it still requires the homeowner or landscape contractor responsible for the maintenance of commercial sites to return to each site a number of times a year to manually reprogram each controller, in addition to their normal maintenance responsibilities. The SNWA estimates that near full compliance to their mandated watering schedules (without any smart controller usage) would save at least 10% of the entire annual water needs (residential, commercial and industrial) in Clark County Nevada, which includes Las Vegas. This is important because the cost of upgrading the infrastructure or importing water from the Northern-Sierra Nevada could run into the billions of dollars.
Based upon a study sponsored by the Irrigation Association, most irrigation users are not willing to or are incapable of changing their schedules as required during the course of the year. It is therefore desirable to provide inexpensive, easily installable, easily programmable, automated, non-smart, add-on irrigation control methods and apparatus that operate independent of environmental conditions, system hydraulics, or controller size or model that automate implementation of governmentally established watering restrictions. This approach has the potential to save hundreds of times more real water than any existing smart controller.
In addition, in locations with rapidly increasing population, the device would alleviate the pumping and delivery problems of the available water thereby also saving energy pumping costs. Energy and water are two resources that are critical to any community that need to be conserved and managed. Energy conservation has been promoted by electric utilities in many communities for years in the following ways:                1. In California in the 1990's, Pacific Gas and Electric and Southern California Edison offered programs to agricultural customers that significantly reduced their electric rates if they abstained from using their irrigation pumps during certain times of the day.        2. Electric utility companies offered rate incentives for residences that reduced their power usage during peak times of the day, particularly in the summer. It was less expensive to offer power credits or reduced rates than to build new power plants and lines.        3. These power utility companies also had “rolling brownouts” that selectively turned off parts of cities to save energy during heat waves that exceeded the power grid demand capabilities of power generation and delivery.        4. Today, certain electric companies are proposing to control thermostats during certain times of the day to help conserve energy. This would be presumably accomplished with the installation of a wireless device that can control either the heater/air conditioner, or the temperature setting itself.        
All of the above attempts are exclusively related to energy conservation during certain times of the day. It would therefore be desirable to conserve both water and energy by reducing the use of additional pumps or larger horsepower pumps by providing an inexpensive, easily installable, easily programmable, non-smart, automated, add-on irrigation control methods and apparatus to automate implementation of governmentally established watering restrictions.
2. Description of the Prior Art
A number of modules or add-on devices are available which attach to existing conventional controllers to make them smart and theoretically save water. Among them is the invention disclosed in U.S. Pat. No. 6,892,114. This patent discloses monitoring of the inrush and holding currents output from the controller in order to “learn” the initial programmed station run times. After calculating desired run times from supplied environmental parameters, the controller outputs are cut off at the new calculated time. The cut offs fluctuate from day to day depending on the environmental parameters and the calculations. In another embodiment, ET values are accumulated until a minimum threshold value is reached before irrigation occurs. In U.S. Pat. No. 6,895,987, an irrigation scheduler automatically modifies irrigation schedules of installed irrigation controllers to affect irrigating of the landscape based on the water requirements of the landscape plants, and calculates a daily ET value which is then used to control the output of the controller. Publication No. 2004/0039489 describes wireless transmission of various environmental data such as temperature, humidity, solar radiation, wind, and rainfall to calculate an ET value in a module attached to the output of an irrigation controller which then modifies its schedule. This design is manufactured by Weather Reach and commercially marketed by Rain Bird.
The August 2007 edition of Weather and Soil Moisture Based Landscape Irrigation Scheduling Devices (published by the U.S. Dept. of the Interior, Bureau of Reclamation) describes a number of currently manufactured “smart” irrigation control devices, including: a weather station by Hunter Industries which provides environmental data to a module attached to their controllers which calculates a daily ET and provides it to the controller which then determines if, when, and how much to irrigate; add-on modules made by Water2Save, Micromet, and Eco Research which are dependent upon environmental or ET-based data to govern various controller outputs or irrigation schedules. Ground moisture sensors as add-on devices are also disclosed in the Bureau of Reclamation publication such as those provided by Irrometer, Acclima, Dynamax, Lawn Logic, and Watermonics. These devices measure soil moisture to determine the need for irrigation.
It is apparent from the foregoing that a number of “smart” add-on modules are currently available that are designed to manage the outputs of irrigation controllers based on changing environmental conditions. However, all of these inventions are dependent upon environmental factors or ground moisture to calculate or determine the time, duration, or frequency of irrigation cycles. In contrast, the present invention does not use real time environmental data, any additional equipment such as weather stations, stored historical weather data, transmitted or calculated weather data, or any form of ET to control an irrigation controller's output(s), nor does it monitor the outputs of existing controllers, or adjust the irrigation schedule based upon the landscape vegetation plant needs.